Thin film MR head and method of making wherein pole trim takes place at the wafer level

ABSTRACT

A method of manufacturing a thin film merged magnetic head including an inductive write structure and a magnetoresistive sensor uses a patterned protection layer to protect a second shield/bottom pole layer in regions spaced from the pole tip of the inductive write structure. A window is provided in the protection layer. During manufacture, the configuration comprises a first shield layer, a magnetoresistive element, a second shield layer serving as a bottom pole, a protection layer, a protection window, a write gap, a top pole, and a pole tip structure. The use of a protection layer and window results in the formation of channels in the second shield layer adjacent to a pedestal that supports the inductive write structure. The channels prevent magnetic flux from extending toward the second shield layer beyond the width of the pole tip structure. This structure reduces side writing with a consequent improvement in off-track performance. The width of the second shield layer allows the magnetoresistive element to be shielded.

FIELD OF THE INVENTION

This invention relates to a merged thin film magnetic head incorporatingan inductive head for writing data and a magnetoresistive (MR) sensor toread recorded data and in particular to a method of trimming to alignthe top and bottom poles at write gap of the write inductive head atwafer level with minimized impact on read sensor performance.

DESCRIPTION OF THE PRIOR ART

Personal computers store data on hard disk drives which consist of oneor more magnetic disks that store data. Data are written to and readfrom the disks by read/write heads, one on each side of a single disk.These read/write heads determine the density of data that can be storedon a given size disk. The heads are more difficult and costly tomanufacture than the disks, involving a variety of rigorous thin filmdeposition and patterning steps. The trend in the computer industry istoward higher densities with an increasing number of bits per squareinch. Concurrently with this trend is the trend toward a high data rate.

In a disk drive, bits are stored magnetically, with a binary one or zerobeing determined by the direction of a magnetic field recorded on thesurface of the disk. The read/write head writes data to the disk byswitching the magnetic field in a given area, and it reads the data bysensing the direction of the recorded magnetic field. Conventionalread/write heads perform both the write function and the read functionwith a single inductive head. An electrically conductive coil is used toinduce a magnetic field at a transducing gap to write information on amagnetic disk. The same coil is used during the read mode to sense themagnetic field recorded on the disk.

A problem with inductive heads is that a large number of coil turns isrequired to sense read signals. The high coil turns increase headresponse time and therefore significantly reduce the data rate. As thearea in which a bit is stored gets narrower, necessitated by the desiredhigher write densities and smaller disk sizes, the read pulse signalsare narrower, and experience undesirable noise and therefore are moredifficult to process.

Presently, magnetoresistive (MR) sensor elements are used to readrecorded magnetic signals. The MR sensor measures changes in resistancewhen a magnetic field is applied to change the magnetization of the MRelement. The MR element may operate using either the anisotropic MR(AMR) effect, the spin-valve (SV) effect or the giant magnetoresistive(GMR) effect. By measuring the resistance change, MR heads can be usedfor reading data, but the writing of data must still be performed withinductive heads. Therefore, a "merged" head design is employed whereinread/write heads have both an inductive write head and an MR read head.

In the structure of a merged AMR head, the AMR element consists of threelayers, an MR sensor layer composed of Permalloy (NiFe), a tantalumspacer layer and a NiFe alloy soft adjacent layer (SAL). The SAL has ahigher resistance than the low resistance MR sensor layer and providesan external bias which improves the linearity of the response. The MRsensor is coupled to external read circuits by interconnect leads, forexample a tri-layer sandwich of Ta/Au/Ta, and the distance across theactive MR sensing region defines the read track width.

NiFe shields are provided around the MR element to prevent straymagnetic flux and flux from adjacent tracks from affecting the MRsensor. Between shields, the flux is guided to the MR sensor. Theshields are separated from the MR element and the interconnects by adielectric thin film, such as aluminum oxide, 300-2000 Angstroms thickdepending on linear recording density.

A write head consisting of copper coils, a write gap and a magnetic yokestructure is fabricated on top of the read head. The second shield ofthe MR element also functions as the bottom pole (P1) of the write head.

Specifically, thin film transducers are fabricated with a bottom polelayer P1 and a top pole layer P2, made of Permalloy or other high momentsoft magnetic materials. The pole layers are connected at a back closureto complete a magnetic flux path. Opposite the back closure, anonmagnetic transducing gap is formed at pole tips which are extensionsof the bottom pole layer P1 and top pole layer P2. An electrical coil ofone or more layers separated by insulation is fabricated between the twopole layers. Changes in electrical current supplied to the coil causemagnetic flux changes in the magnetic yoke (P1/P2) at the transducinggap which cause magnetization change representing data bits to beregistered on an adjacent moving magnetic disk. Conversely, flux changesrepresenting data bits on an adjacent magnetic disk may be read by theMR element and processed by read circuitry.

Inductive write head performance is determined in part by the precisionof the alignment between the top pole tip (P1) and the bottom pole tip(P2). This alignment defines the characteristics of the fringe field atthe transducing gap, such as magnetic field strength and gradient. It isimportant that the pole tips have the same width so that flux leakage isminimized. The alignment of pole tips has in the past been attempted bya pole trimming process during fabrication of the inductive thin filmhead.

U.S. Pat. No. 5,578,342 describes a process for producing a conventionalthin film magnetic head which uses the top magnetic pole as aself-aligning mask for partially trimming the bottom magnetic pole. Theyoke and pole tip regions to be trimmed are processed by separate anddistinct photolithographic steps, attempting to achieve noncriticalalignment in the yoke area, while maintaining critical alignment in thepole tip region which includes the transducing gap.

The bottom pole P1 is first deposited on a substrate, P1 being widerthan is desired in the final product. Next an insulating layer isdeposited over P1 which forms the transducing gap. After deposition of acoil assembly surrounded by insulation, a top pole P2 is deposited overan insulating layer. The nonaligned pole tip structure is aligned byusing a material removal process such as ion milling. Ion milling is aprocess in which a surface is bombarded by high energy ions to removethe nonaligned portions of the pole tip. A protective photoresist maskshields the top pole and a portion of the insulating layer at thetransducing gap. The result desired is an aligned pole tip structure. Inpractice, however, the self-masking of the top pole P1 during ionmilling limits the accuracy of the final pole tip structure. Attempts atmore precise masking have improved the process but it still falls short,especially as head designs have become smaller.

As described previously, a merged MR structure combines amagnetoresistive (MR) read head and a separate write head. The MR layeris sandwiched between a bottom shield layer S1 and a top shield layerS2. In this structure, the top shield layer S2 of the MR head is used asthe bottom pole P1 of the write head. A problem with present MR heads ofthis type is that the write head generates significant side-fringefields during writing, caused by flux leakage from the top pole P2 toparts of the bottom pole P1 that extend beyond the desired alignment.Side fringing fields limit track density by limiting the minimum trackwidth possible. When a track written by such a write head is read by theMR element of the read head, off-track performance is poor because ofinterference with adjacent tracks.

In U.S. Pat. No. 5,438,747 a merged MR head is provided which hasvertically aligned side walls to minimize side-fringing and improveoff-track performance. The bottom pole piece P1, which comprises thesecond shield layer S2 of the read head, has a pedestal pole tip with ashort length dimension. A pedestal pole tip with a length as short astwo times the length of the gap layer G optimally minimizes the sidewriting and improves off-track performance. The bottom pole tipstructure of the write head is constructed by ion beam milling using thetop pole tip structure as a mask. The ion beam milling is directed at anangle to the side walls of the top pole tip structure which causes thebottom pole tip structure to be milled with side walls which align withthe top pole tip structure. The ion beam milling can comprise two angledbeams, either sequentially or simultaneously, the first beam performingprimarily a cutting operation and some clean up work while the secondbeam primarily conducts clean up work of the redeposition of the debriscaused by the cutting. In another embodiment, a single angled ion beamcan be employed, provided its angle is within a particular range.

In U.S. Pat. No. 5,438,747, the pole trim structure was performed aftermagnetic yoke formation (P2-defined method). This requires that theeffect of the topography of the coil and insulation structure beovercome in both the photoresist process and the ion milling process.

An alternative approach described in U.S. Pat. No. 5,452,164 describes amethod of forming a pole trimmed structure right after the P1 processstep (P1-definedapproach) where the structure of the device issubstantially planar and therefore a superior patterning process for anarrow track can be obtained. In this method, a photoresist pattern wasused as a hard mask, and ion milling was needed to remove both the toppole tip and the pedestal structure at the bottom shield.

A full pole trimmed structure is desired for better off track capabilityand superior nonlinear transition shift (NLTS) performance when writingonto a magnetic recording medium for high density recording. Thecritical issue for pole trimming in the MR structure of the prior art isintrusion into the S2/P1 layer by the ion milling process. In bothmethods described in U.S. Pat. Nos. 5,438,747 and 5,452,164, the S2/P1layer suffered from damage due to the ion mill trimming process whichcauses write-induced instability during MR reading.

SUMMARY OF THE INVENTION

An object of this invention is to provide an MR head structure withvertically aligned pole tips after yoke formation (P2-defined) and auniformly thick bottom shield layer to thereby reduce side writing forhigh track density.

Another object of this invention is to provide a method of fabricatingan MR head structure with vertically aligned pole tips after yokeformation (P2-defined) and a uniformly thick bottom shield layer tothereby reduce side writing for high track density.

A further object of this invention is to provide an MR head structurewith vertically aligned pole tips after the P1 pole process and beforethe formation of the coil and insulation layer (P1-defined) and auniformly thick bottom shield layer to thereby reduce side writing forhigh track density.

A further object of this invention is to provide a process forprotecting a bottom shield layer from intrusion from an ion millingprocess used to form vertically aligned pole tips.

This invention teaches a method of manufacturing a thin film mergedmagnetic head including an inductive write transducer and amagnetoresistive (MR) sensor wherein an MR read element consisting ofeither AMR, SV or a GMR sensor is sandwiched between a first shieldlayer S1 and a second shield layer S2/P1, wherein P1 serves as thebottom pole of the inductive transducer. In keeping with the invention,a protection layer is deposited on the shield layer S2/P1 in a patternthat forms a window. A pole tip region is formed over the window. Ionbeam milling is used to trim the pole tip region resulting in theformation of channels in the second shield layer S2 adjacent to the poletip region. The thin film magnetic head structure is supported by anonmagnetic substrate.

The invention has the advantage that the trimmed region is limited to alocalized area near the write pole and has minimum damage on S2/P1 sothat the MR read sensor is properly shielded and the inductive writingprocess has the least effect on read performance.

The invention has the further advantage that the structure reduces sidewriting with a consequent improvement in off-track performance andinductive write performance to achieve high density magnetic recording.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 contains both air bearing surface (ABS) and cross-sectional viewsof a prior art MR head structure;

FIGS. 2a-g illustrate a first embodiment of the present inventiondescribing both air bearing surface (ABS) and cross-sectional views ofintermediate structures produced during manufacture of a merged MR head.In this embodiment, a trimmed pole structure is generated at a final toppole process step after the formation of the coil and insulation layer(P2-defined method);

FIG. 3 is a detailed flow diagram of a method of manufacturing theprotection window used in the embodiment shown in FIGS. 2a-g;

FIGS. 4a-4j illustrate a second embodiment of the present inventiondescribing both air bearing surface (ABS) and cross-sectional views ofintermediate structures produced during manufacture of a merged MR head.In this embodiment, a trimmed pole structure was generated right afterthe bottom pole P1 process and prior to the formation of the coil andinsulation layer (P1-definedapproach).

FIG. 5 is a detailed flow diagram of a method of manufacture theprotection window used in the embodiment shown in FIGS. 4a-4j;

FIGS. 6a-d illustrate a method of forming a protection window mask; and,

FIGS. 7a-7c illustrate a method of a pole trim process using a combinedion milling and reactive ion milling process.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, a read head formed on a substrate includes an MR element 100sandwiched between a first shield (S1) layer 102 and second shield (S2)layer 104. The MR read element consists of a sensing element, a domainstabilization layer and a bias layer where the sensing element is madeof either AMR, SV or GMR material. The domain stabilization layer isused to suppress Barkhausen noise. The bias layer ensures that thesensor element works in the linear region and has the highestsensitivity. The second shield (S2) layer 104 of the read head alsoserves as the bottom pole P1 of a write head. The inductive write headincludes the bottom pole P1 and a top P2 pole 106. An insulatingtransducing write gap layer 108 is sandwiched between the P1 and P2layers. The large width of the second shield S2 layer 104 beyond thesides 114, 116 of the pole tip region causes flux to extend toward thesecond shield layer S2 beyond the width of the pole tip element P1. Thisflux causes side writing which degrades off-track performance. Inpractice this problem is overcome by ion milling the second shield layeron either side of the write gap to create a pedestal which is anextension of the bottom pole piece P1. The width of the second shieldlayer S2 is chosen to shield the MR element.

In practice, during ion milling to create the pedestal, the secondshield layer S2 becomes sloped when forming the pole trim structures.Due to shadowing of the pole P2, S2/P1 104 becomes sloped and is thin atthe outside regions 118, 120, away from the write pole. This isundesirable as the thin structure reduces the effect of shielding at theoutside regions. Ideally, the structure would be flat as indicated bythe broken lines in FIG. 1.

Method of Manufacturing A Magnetoresistive (MR) Head Structure

The preferred method of the present invention is to fabricate a P2defined write structure. In a P2 defined type of write structure, thewrite pole structure is formed after the coil layer, insulation and P2.The alternative embodiment of this invention is for a P1 defined writestructure. In a P1 defined type of write structure the write polestructure is formed before the coil layer, insulation and P2.

A high Bsat layer at the bottom P2 tip and at the top of pedestalstructure is provided near the write gap. High Bsat is a high momentsoft magnetic metal which can be made of Ni_(100-x) Fe_(x), (X=35, 45,and 55), CoZrX (X=Ta, Cr, Ru, Rh) and FeNX (X=A1, Ta, Rh).

FIGS. 2a-g provide a detailed description of a first embodiment with aP2-defined method. A first shield S1 layer 200 is provided upon which asensing element 202 and a pair of lead connects 205 are deposited (FIG.2a). The MR read element consists of a sensing element, a domainstabilization layer and a bias layer where the sensing element can bemade of either one of AMR, SV and GMR materials. A second shield S2layer 204 is deposited on the MR element (FIG. 2b). The MR element istherefore diposed between the first shield S1 layer 200 and the secondshield S2 layer 204 and is separated from both shields by a first readgap 201 and a second read gap 203. The second shield layer 204 will alsoserve as the bottom pole piece P1 of a write head, and is designated asS2/P1. The second shield material can be made of either Permalloy, or abilayer structure of Permalloy and high Bsat soft magnetic material. Aprotection layer 206 is deposited on the S2/P1 shield layer 204 (FIG.2c). The preferred protection layer is made of a composite layer ofdielectric material such as Al₂ O₃, SiO₂ or Si₃ N₄, and nonmagneticmaterials such Ta, W and Mo. The composite layer is then patterned toform a window 208. A write gap layer 210 is deposited on the protectionlayer (FIG. 2d). Following the write gap process, the first insulationlayer 230, coil 232 and the second insulation layer 234 are fabricated(FIG. 2e). Optionally, a multiple layer coil structure can befabricated. After the formation of the coil and insulation structure, ahigh Bsat layer 212 is deposited on the write gap layer 210 andinsulation 230 and 234. A top P2 pole 214 consisting of either plated orsputtered magnetic films is then deposited on the Bsat layer (FIG. 2f).Ion beam milling is employed to trim the pole tip in order to achievevertical side walls (FIG. 2g). In the case of sputtered high Bsatmaterials used for both pole tip and yoke structure, a photoresist orother hard mask can be used for the ion milling mask. The protectionlayer 206 functions during ion milling to create a pedestal 216 which isan extension P1/P2 of the bottom pole P1.

Another embodiment can be extended to a P1-defined structure. The methodis described in detail in FIGS. 4a-4j. Similar process steps as thefirst embodiment of FIG. 2 are used for this embodiment up to write gapformation (FIG. 4a-4d). Following the write gap formation process, ahigh Bsat layer 312 is deposited on the write gap 210 and a top pole tipstructure 314 is formed (FIGURE 4e). A combination of ion beam millingand reactive ion milling is employed to trim the pole tip in order toachieve vertical side walls (FIG. 4f). In the case of sputtered highBsat materials used for both pole tip and yoke structure, a photoresistor other hard mask can be used for ion milling mask. The protectionlayer 206 functions during ion milling to create a pedestal 216 which isan extension P1/P2 of the bottom pole piece P1. After trimmed poleformation, a dielectric insulation layer such as Al₂ O₃, SiO₂ and Si₃ N₄is deposited (FIG. 4g) and subsequently the structure is planarized bychemical mechanical polishing (FIG. 4h). The planarized dielectricmaterials will function as the first insulation for coil 322 (FIG. 4i).Optionally, a multiple layer coil structure can be fabricated usingadditional coil and insulation. After the formation of the coil andinsulation structure, the top yoke structure 324 is fabricated (FIG.4j).

As shown in FIGS. 2g and 4j, the use of a protection layer results inthe formation of channels 209/211 and 309/311, in the second shield S2layer 204 adjacent to the pole tip region. The channels prevent fluxfrom extending toward the second shield S2 layer 204 beyond the width ofthe pole tip element P1/P2. This structure reduces side writing with aconsequent improvement in off-track performance. The width of the secondshield S2 layer 204 is such that the MR element is shielded.

Method Of Forming A Window

For either a P1 defined type of write structure or a P2 defined type ofwrite structure a protection layer 206 and window 208 (FIG. 2d) isformed in accordance with the teachings of the present invention. Afirst embodiment is described with reference to FIG. 6.

A trilayer structure formed with a thin Ta (100-300 Å) layer 402, an Al₂O₃ layer (5000-15000 Å) 404 and a thick Ta film (2000-10000 Å) 406 isformed on top of S2/P1 400 (FIG. 6a). A protection window mask 408 isformed by a photoresist process (FIG. 6b). Ion milling is then used toremove the top thick Ta film 410 (FIG. 6c). When Al₂ O₃ is exposed, awet etch process or reactive process can be applied to remove the Al₂ O₃material 412 with bottom thin Ta film 414 as etch stop (FIG. 6d). Thethin Ta etch stop layer can be removed by sputter etch during depositingthe write gap.

The top thick Ta film is chosen because of its high ion millingselectivity with respect to transition metal and alloys used for polematerials. Other types of materials such as TaW, W can also be used. Thefurther advantage of using Ta materials is its high selectivity to writegap Al₂ O₃ in an Ar/fluorine reactive ion milling process.

Other types of an insulating dielectric material such as Al₂ O₃, SiO₂ orSi₃ N₄ can be used for forming a window. This window can be patterned byeither a liftoff technique or an etch back technique.

Pole Formation Process

After a protection layer is formed, the P2 pole structure is formed. Thepreferred method to form the pole structure is illustrated in FIG. 7.

(1) Ion mill (physical bombardment) to remove either high Bsat layer orseed layer 506 completely. A hard mask 508 may be used made of eitherphotoresist or pole materials.

(2) A reactive ion beam etch (RIBE) with Ar/fluorine chemistry isapplied to remove write gap 504. The preferred chemistry is Ar/CHF3.

(3) After removing the write gap, ion mill is used to form pedestalstructure 502 in S2/P1 layer 500.

Magnetoresistive (MR) Head Structure

The final structure of the first embodiment using a P2 defined methodshown in FIG. 2g is comprised of a first shield layer 200, an MR readelement 202, a second shield layer 204 that also functions as a bottompole P1, a P1/P2 region 216, an extra write gap 218, a write gap 220,and a top pole 222. The use of a protection layer and window results inthe formation of channels 209, 211, in the second shield layer (S2) 204near the sides of the pole tip region 222.

The final structure of the embodiment using a P1 defined method shown inFIG. 4j is comprised of a first shield layer 200, an MR read element202, a second shield layer 204 that also functions as a bottom pole P1,a P1/P2 region 316, an extra write gap 318, a write gap 320, and a P2pole tip piece 324. A coil 322 surrounded by insulation is disposedbetween the lower P1 pole and top P2 pole layers. A top P2 cap 324,which is wider than the P2 pole tip, is connected to a yoke. The use ofa protection layer and window results in the formation of channels 309,311, in the second shield layer (S2) 204 near the sides of the pole tipregion.

The channels of both structures prevent flux from extending toward thesecond shield layer S2 beyond the width of the pole tip element P1/P2.This structure reduces side writing with a consequent improvement inoff-track performance. The width of the second shield layer S2 is suchthat the MR element is shielded.

It will be understood by those skilled in the art that the MR elementdescribed herein can be any element operated using an an isotropic MR(AMR) effect, spin-valve (SV) effect, or giant magnetoresistive (GMR)effect, or any other structures that are based on the phenomenon thatthe resistance of magnetic conductors change when a magnetic field isapplied to change the magnetization of the element.

It will be understood by those skilled in the art that the ion beamprocess may be a combination of Ar ion beam milling process and Ar/CHF₃reactive ion beam milling process, and that other fluorine chemistrysuch as CF₄ and CH₂ F₂ can also be applied.

It will also be understood by those skilled in the art that theprotection layer may be any suitable nonmagnetic material, such as, butnot limited to Ta, Al₂ O₃, Ta film, a combination of thin Ta (100-300Å), Al₂ O₃ (5000-15000 Å) and thick Ta film (2000-10000 Å), or othernon-magnetic material such as SiO₂, Si₃ N₄, TaW, and Cr.

The top thick Ta film is chosen because of its high ion millingselectivity with respect to transition metal and alloys used for polematerials. Other types of materials such as TaW, W can also be used. Thefurther advantage of using Ta materials is its high selectivity to writegap Al₂ O₃ in Ar/fluorine reactive ion milling process. Other types ofan insulating dielectric material such as Al₂ O₃, SiO₂ or Si₃ N, can beused for forming a window. This window can be patterned by either aliftoff technique or an etch back technique.

What is claimed is:
 1. A method of making a merged thin film magnetichead including an inductive write transducer and a magnetoresistivesensor, said inductive transducer including a write pole structurehaving a bottom pole layer and a top pole layer comprising the stepsof:depositing a first magnetic shield on a substrate; depositing asecond magnetic shield layer, said second magnetic shield layer servingas a bottom pole of said write pole structure; forming a protectionlayer and a window over said second magnetic shield layer in a patternfor protecting regions of said second magnetic shield layer from saidwrite pole structure and forming a pedestals and channels recessed intosaid second magnetic shield layer on each side of said pedestal, whereinsaid pedestal supports said write pole structures forming a write gaplayer over said protection layer; depositing a top pole layer over saidsecond magnetic shield layer; and directing an ion beam at said top polelayer for shaping said pedestal such that said pedestal extends intosaid second magnetic shield layer.
 2. The method of claim 1 wherein:saidmagnetoresistive sensor is either an anisotropic magnetosresistiveelement, a spin-valve element, or a giant magnetoresistive element. 3.The method of claim 1 wherein:said protection layer is nonmagnetic. 4.The method of claim 1 wherein:said protection layer consists essentiallyof thin Ta (100-300 Å), Al₂ O₃ (5000-15000 Å) and thick Ta film(2000-10000 Å).
 5. The method of claim 1 wherein:said protection layerconsists essentially of a nonmagnetic material such as SiO₂, Si₃ N₄,TaW, and Cr.
 6. The method of claim 1 wherein:said protection pattern isformed by an etch back technique.
 7. The method of claim 1 wherein:saidprotection pattern is formed by a lift-off technique.
 8. The method ofclaim 1 wherein:said step of directing an ion beam comprises acombination of an Ar ion beam milling process and an Ar/CHF₃ reactiveion beam milling process.
 9. A method of manufacturing a merged thinfilm magnetic head including an inductive write transducer and amagnetoresistive sensor, said inductive transducer including a writepole structure having first and second poles including first and secondpole tips respectively for defining a write gap comprising the stepsof:forming first and second magnetic shield layers, said second magneticshield layer serving as the first pole; forming a magnetoresistivesensor between said first and second magnetic shield layers, includingthe steps of:forming a protection layer and window above said secondmagnetic shield layer in a pattern that forms a protection window;forming a pole tip over said window; directing an ion beam to trim saidpole tip region for forming channels recessed in said second shieldlayer adjacent to said pole tip; forming an insulated coil assemblyafter pole tip formation; and forming a magnetic yoke structure.
 10. Themethod of claim 9 wherein said magnetoresistive read sensor is eitheranisotropic magnetoresistive, spin-valve or a giant magnetoresistiveelement.
 11. The method of claim 10 wherein said protection layer isnonmagnetic.
 12. The method of claim 10 wherein said protection layerconsists of thin Ta (100-300 Å), Al₂ O₃ (5000-15000 Å) and thick Ta film(2000-10000 Å).
 13. The method of claim 9 wherein said protection windowis formed by an etch back technique.
 14. The method of claim 9 whereinsaid protection window is formed by a lift-off technique.
 15. The methodof claim 9 wherein said pole tip over said protection window is formedprior to forming said insulated electrical coil.
 16. The method of claim9 wherein said coil is formed as a single layer coil.
 17. The method ofclaim 9 wherein said coil is formed as a multilayer coil.
 18. The methodof claim 9 wherein said step of directing an ion beam is a combinationof an Ar ion beam milling process and an Ar/CHF₃ reactive ion beammilling process.
 19. The method of claim 9 wherein said magnetic yoke isformed after the formation of said insulated coil.
 20. A method ofmanufacturing a magnetoresistive head structure in which amagnetoresistive read head element is disposed between a first shieldlayer and a second shield layer, comprising the steps of:depositing aprotection layer on said second shield layer in a pattern that forms aprotection window; forming an insulated coil assembly; forming amagnetic yoke structure and a magnetic pole tip, said magnetic pole tipbeing in a region over said window; and directing an ion beam fortrimming said pole tip region to form channels in said second shieldlayer adjacent to said pole tip.